1. Field of the Invention
The present invention relates to collapsible containers having pallet-type bases with upright container walls pivoted to the base and adapted to be moved to a folded position on the pallet for return transport in the empty condition. This type of container is designed for fork lift handling and is adaptable for a wide variety of general utility purposes ranging from the transport or storage of packaged goods to bulk commodities such as produce and the like.
2. The prior Art
Collapsible containers having foldable side walls for return shipping are well known in the prior art and are subject to a wide range of uses. Such containers range in size from rather large capacity cargo container units for rail and shipboard handling to rather small light-weight containers designed for such commodities as bakery goods and farm produce. Examples of the latter type of collapsible containers made from molded flexible plastic with integral hinge structures and snap fitting joints are contained in the Saunders et al U.S. Pat. Nos. 3,870,185 and 3,874,546 and the Waller U.S. Pat. No. 4,320,845. These containers may be characterized as being rather light weight small capacity structures and are designed for carrying light weight fragile or frangible articles such as loaves of bread or egg cartons.
Larger bin structures for general utility use, of the type capable of being handled by a fork lift, have also been constructed from molded rigid plastic materials. This type of container may be characterized as a pallet base container. The Kardell U.S. Pat. No. 4,057,165 is one such device wherein flexible plastic hinge members permit the side walls to be folded onto the pallet base. The Vande Drink U.S. Pat. No. 4,235,345 and the Te-Chi Hsu U.S. Pat. No. 4,300,695 are further examples of injection molded collapsible containers usable for general utility purposes. The Te-Chi Hsu patent is exemplary of injection molded plastic structures utilizing metal hinge pins to accomplish the hinging function between plastic panels. The metal hinge pins are designed to withstand lateral loads and are intended to provide the necessary strength to the structure.
Generally speaking, the problem encountered with prior art efforts to design molded plastic containers for heavy duty purposes has been the difficulty in providing a pallet type base with foldable walls which, when erected, are strong enough to carry extremely heavy loads such as machine parts or heavy metal objects for instance. Although it is well known in the art that hinge members may be molded integrally with the side and bottom walls and simply snapped together to form collapsible containers, the resulting structure will not stand up under heavy use. On the other hand, if such devices as metal clips, metal hinge pins or other reinforcing members are added to the collapsible multi-paneled plastic structure the parts usually become separated and lost when the container is collapsed for return shipment. In addition, such designs involving multiple separate parts of diverse materials are extremely expensive to manufacture and usually too cumbersome to be practical. Other considerations such as replacement of worn out parts and the ability to keep the container structure clean have plagued the industry for years.